THE STRUCTURE AND SYNTHESIS OF 4-OXYPANNARIC ACID 2-METHYL ESTER, A DIBENZOFURAN FROM THE LICHEN LEPROLOMA-DIFFUSUM

The structure of the major dibenzofuran present in the lichen Leprolom a diffusum has been shown to be that of 4-oxypannaric acid 2-methyl es ter (2-methyl hydrogen ydroxy-1,7-dimethyldibenzofuran-2,6-dicarboxyla te) (2). The structure of (2) was confirmed by total synthesis, achiev ed through a biomimetic-type approach using palladium(ii) acetate in t he key cyclization step. Partial synthesis of the corresponding dimeth yl ester (8) was effected starting from natural pannaric acid 6-methyl ester (6).